Index: COFF/InputFiles.cpp
===================================================================
--- COFF/InputFiles.cpp
+++ COFF/InputFiles.cpp
@@ -339,8 +339,8 @@
 }
 
 void BitcodeFile::parse() {
-  Obj = check(lto::InputFile::create(
-      MemoryBufferRef(MB.getBuffer(), Saver.save(MB.getBufferIdentifier()))));
+  Obj = check(lto::InputFile::create(MemoryBufferRef(
+      MB.getBuffer(), Saver.save(ParentName + MB.getBufferIdentifier()))));
   for (const lto::InputFile::Symbol &ObjSym : Obj->symbols()) {
     StringRef SymName = Saver.save(ObjSym.getName());
     auto Flags = ObjSym.getFlags();
Index: test/COFF/Inputs/bar.ll
===================================================================
--- /dev/null
+++ test/COFF/Inputs/bar.ll
@@ -0,0 +1,6 @@
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define void @bar() {
+  ret void
+}
Index: test/COFF/thinlto-archives.ll
===================================================================
--- /dev/null
+++ test/COFF/thinlto-archives.ll
@@ -0,0 +1,22 @@
+; RUN: rm -fr %T/thinlto-archives
+; RUN: mkdir %T/thinlto-archives %T/thinlto-archives/a %T/thinlto-archives/b
+; RUN: opt -thinlto-bc -o %T/thinlto-archives/main.obj %s
+; RUN: opt -thinlto-bc -o %T/thinlto-archives/a/bar.obj %S/Inputs/lto-dep.ll
+; RUN: opt -thinlto-bc -o %T/thinlto-archives/b/bar.obj %S/Inputs/bar.ll
+; RUN: llvm-ar crs %T/thinlto-archives/a.lib %T/thinlto-archives/a/bar.obj
+; RUN: llvm-ar crs %T/thinlto-archives/b.lib %T/thinlto-archives/b/bar.obj
+; RUN: lld-link /out:%T/thinlto-archives/main.exe -entry:main \
+; RUN:     -subsystem:console %T/thinlto-archives/main.obj \
+; RUN:     %T/thinlto-archives/a.lib %T/thinlto-archives/b.lib
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+declare void @bar()
+declare void @foo()
+
+define i32 @main() {
+  call void @foo()
+  call void @bar()
+  ret i32 0
+}